A silicon wafer etching using a burst pulse high-power inductively coupled plasma (ICP) is investigated. A 200 μs wide burst of a 157 kHz power supply is employed to generate ICP with a repetition rate of 50 Hz. A rectangular pulsed voltage synchronized with the burst power supply is applied upto 1 kV at the wafer. Mixed gas of argon (Ar) and tetrafluoromethane (CF 4 ) is supplied into the vacuum chamber. The plasma density and electron temperature are 10 19 m −3 and 2.8 eV where the wafer is, respectively. In the case of Ar plasma, the silicon etching rate is 0.01 μm min −1 with 1000 V negative bias. The etching rate increases to 0.23 μm min −1 by adding CF 4 into Ar and increases linearly with increasing the bias voltage. The target current and emission intensity of Ar + and F * are depended on bias voltage from −300 to −1000 V. The etching rate sharply increases by increasing CF 4 content from 0% to 10%, and it becomes almost constant at 10%. The dependency of emission intensity of F * on CF 4 content is similar to the dependency the etching rate.
The behavior of argon inductively coupled plasma (ICP) driven by a 150 kHz-band high-voltage pulse burst is investigated using the mutual induction circuit model and a spatially averaged global model. A high-voltage of 4 kV was applied to the 50-turns solenoid coil to generate a magnetic field in the 52 mm inner diameter glass tube. The coil current of 47 A flowed into the solenoid coil with 83 Ω of equivalent load impedance before the plasma ignition. The coil voltage and current decreased to 2.0 kV and 30 A with plasma ignition. The measured waveforms of the coil voltage and current were used to obtain the electrical characteristics based on the equivalent circuit with the mutual induction circuit model. The magnetic coupling factor was obtained to be in range from 0.6 to 0.7 at various gas pressers and input power. The characterization of the ICP was analyzed using the global model with 200 μs width burst pulse. The electron temperature and plasma density were obtained as 2–3 eV and 1019 m−3, respectively, at an input power of several kilo-watts. These values were almost consistent with those measured using a double probe. The densities of the exited argon atom were estimated to be 1017 m−3.
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